The present invention relates in general to lenses and more particularly to a lens having non-linear distortion characteristics.
The typical remote viewing system utilizes a television camera at the remote location, some type of projector at the observer location, and a television transmitting system linking the two. These viewing systems fall far short of duplicating the visual characteristis of the human eye in that they have extremely limited fields of view or else poor resolution in a large field of view.
In particular, for any fixed angular resolution (measured in minutes of arc) and frame rate (usually 30 Hz or frames/sec.) a definite relationship exists between field of view and bandwidth for transmitting that field of view. For example, commercial television, which utilizes a 525 line raster traced 30 times per second, operates on a bandwidth of 3.93 MHz. To match the resolution of the human eye, which is one minute of arc along its foveal or optical axis, the field of view for commercial television must be restricted to less than 10.degree. (see FIG. 1). On the other hand, if the field of view is increased to about 180.degree., which is the field of view for the human eye, the bandwidth must be increased to 1000 Mhz to maintain one minute of arc resolution over the entire field. This demands a raster of 10,000 lines and is far in excess of the capabilities of current television systems.
Indeed, the most advanced television currently available utilizes an 875 line system and requires a bandwidth of 10.9 Mhz. This provides a field of view of about 20.degree. with one minute arc resolution throughout the entire field, which is far less than the 180.degree. field of view possessed by the human eye.
From the foregoing, it is clear that present television viewing systems present a dilemma. If the field of view is sufficient to encompass all possible locations of interest, resolution is so low that detection or clear observation is impossible. On the other hand, if the resolution is adequate to insure that the objects will be seen clearly, the field of view is quite limited and many objects of interest are located outside of the field of view.
In a sense the human eye provides a solution for the foregoing dilemma. The human eye possesses high optical acuity along and in the vicinity of its foveal or optical axis, but the acuity diminishes outwardly therefrom. In other words, the eye distinguishes fine detail directly in front of it, but not to the sides. This characteristic is not derived from the shape of the eye lens, but instead results from the fact that most of the optical fibers for the eye are concentrated in the vicinity of the optical axis. Hence, only along the optical axis does the eye possess one minute of arc resolution. The resolution becomes progressively less toward the periphery of the field of vision (see FIG. 2). Nevertheless, the resolution in the peripheral area is sufficient to detect the presence of many objects in that area as well as much movement in that area. Of course, when the eye detects anything of interest in the peripheral areas, the head or eye is immediately moved to bring the foveal axis to the thing of interest and thereby provide a clearer image of it.